1. Field of the Invention
The present invention relates to a process for preparing an enzyme capable of inactivating cytosolic aspartate aminotransferase (EC 2.6.1.1, systematic name=L-Aspartate: 2-oxoglutarate aminotransferase; another name=glutamic-oxaloacetic transaminase; hereinafter referred to as "AST") isozyme, by cultivating a strain of genus Streptomyces.
2. Description of the Prior Art
AST isozymes occur in the liver, myocardium, brain, skeletal muscle, kidney and the like, and have been known as enzymes which catalyze the following reaction: EQU L-Aspartate+2-Oxoglutarate .revreaction.Oxaloacetate+L-Glutamate
The AST isozymes include two kinds of isozymes different in localization, one being a cytosolic AST isozyme (hereinafter referred to as "s-AST") and the other a mitochondrial AST isozyme (hereinafter referred to as "m-AST"). Fractional determination of these isozymes is useful for the clinical diagnosis of hepatitis, myocardial infarction, etc.
On the susceptibility of AST isozymes to proteases, there are reports by E. Sandmeier et al. (J. Biol. Chem., Vol. 255, 10284-10289 (1980)) and by D. E. Metzler et al., (Federation Proceedings, Vol. 41, 2432-2436 (1982)). E. Sandmeier et al. have reported that trypsin limitedly cleaved m-AST to inactivate it, and in a preliminary experiment a similar proteolytic cleavage of s-AST was observed. D. E. Metzler et al. have described that m-AST was inactivated by trypsin though more slowly than s-AST.